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/* vi: set sw=4 ts=4: */
/* mkswap.c - format swap device (Linux v1 only)
*
* Copyright 2006 Rob Landley <rob@landley.net>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//config:config MKSWAP
//config: bool "mkswap (5.8 kb)"
//config: default y
//config: help
//config: The mkswap utility is used to configure a file or disk partition as
//config: Linux swap space. This allows Linux to use the entire file or
//config: partition as if it were additional RAM, which can greatly increase
//config: the capability of low-memory machines. This additional memory is
//config: much slower than real RAM, but can be very helpful at preventing your
//config: applications being killed by the Linux out of memory (OOM) killer.
//config: Once you have created swap space using 'mkswap' you need to enable
//config: the swap space using the 'swapon' utility.
//config:
//config:config FEATURE_MKSWAP_UUID
//config: bool "UUID support"
//config: default y
//config: depends on MKSWAP
//config: help
//config: Generate swap spaces with universally unique identifiers.
//applet:IF_MKSWAP(APPLET(mkswap, BB_DIR_SBIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_MKSWAP) += mkswap.o
//usage:#define mkswap_trivial_usage
//usage: "[-L LBL] BLOCKDEV [KBYTES]"
//usage:#define mkswap_full_usage "\n\n"
//usage: "Prepare BLOCKDEV to be used as swap partition\n"
//usage: "\n -L LBL Label"
#include "libbb.h"
#include "common_bufsiz.h"
#if ENABLE_SELINUX
static void mkswap_selinux_setcontext(int fd, const char *path)
{
struct stat stbuf;
if (!is_selinux_enabled())
return;
xfstat(fd, &stbuf, path);
if (S_ISREG(stbuf.st_mode)) {
security_context_t newcon;
security_context_t oldcon = NULL;
context_t context;
if (fgetfilecon(fd, &oldcon) < 0) {
if (errno != ENODATA)
goto error;
if (matchpathcon(path, stbuf.st_mode, &oldcon) < 0)
goto error;
}
context = context_new(oldcon);
if (!context || context_type_set(context, "swapfile_t"))
goto error;
newcon = context_str(context);
if (!newcon)
goto error;
/* fsetfilecon_raw is hidden */
if (strcmp(oldcon, newcon) != 0 && fsetfilecon(fd, newcon) < 0)
goto error;
if (ENABLE_FEATURE_CLEAN_UP) {
context_free(context);
freecon(oldcon);
}
}
return;
error:
bb_perror_msg_and_die("SELinux relabeling failed");
}
#else
# define mkswap_selinux_setcontext(fd, path) ((void)0)
#endif
/* from Linux 2.6.23 */
/*
* Magic header for a swap area. ... Note that the first
* kilobyte is reserved for boot loader or disk label stuff.
*/
struct swap_header_v1 {
/* char bootbits[1024]; Space for disklabel etc. */
uint32_t version; /* second kbyte, word 0 */
uint32_t last_page; /* 1 */
uint32_t nr_badpages; /* 2 */
char sws_uuid[16]; /* 3,4,5,6 */
char sws_volume[16]; /* 7,8,9,10 */
uint32_t padding[117]; /* 11..127 */
uint32_t badpages[1]; /* 128 */
/* total 129 32-bit words in 2nd kilobyte */
} FIX_ALIASING;
#define NWORDS 129
#define hdr ((struct swap_header_v1*)bb_common_bufsiz1)
#define INIT_G() do { setup_common_bufsiz(); } while (0)
struct BUG_sizes {
char swap_header_v1_wrong[sizeof(*hdr) != (NWORDS * 4) ? -1 : 1];
char bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
};
/* Stored without terminating NUL */
static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mkswap_main(int argc UNUSED_PARAM, char **argv)
{
int fd;
unsigned pagesize;
off_t len;
const char *label = "";
INIT_G();
/* TODO: -p PAGESZ, -U UUID */
getopt32(argv, "^" "L:" "\0" "-1"/*at least one arg*/, &label);
argv += optind;
fd = xopen(argv[0], O_WRONLY);
/* Figure out how big the device is */
len = get_volume_size_in_bytes(fd, argv[1], 1024, /*extend:*/ 1);
pagesize = getpagesize();
len -= pagesize;
/* Announce our intentions */
printf("Setting up swapspace version 1, size = %"OFF_FMT"u bytes\n", len);
mkswap_selinux_setcontext(fd, argv[0]);
/* hdr is zero-filled so far. Clear the first kbyte, or else
* mkswap-ing former FAT partition does NOT erase its signature.
*
* util-linux-ng 2.17.2 claims to erase it only if it does not see
* a partition table and is not run on whole disk. -f forces it.
*/
xwrite(fd, hdr, 1024);
/* Fill the header. */
hdr->version = 1;
hdr->last_page = (uoff_t)len / pagesize;
if (ENABLE_FEATURE_MKSWAP_UUID) {
char uuid_string[32];
generate_uuid((void*)hdr->sws_uuid);
bin2hex(uuid_string, hdr->sws_uuid, 16);
/* f.e. UUID=dfd9c173-be52-4d27-99a5-c34c6c2ff55f */
printf("UUID=%.8s" "-%.4s-%.4s-%.4s-%.12s\n",
uuid_string,
uuid_string+8,
uuid_string+8+4,
uuid_string+8+4+4,
uuid_string+8+4+4+4
);
}
safe_strncpy(hdr->sws_volume, label, 16);
/* Write the header. Sync to disk because some kernel versions check
* signature on disk (not in cache) during swapon. */
xwrite(fd, hdr, NWORDS * 4);
xlseek(fd, pagesize - 10, SEEK_SET);
xwrite(fd, SWAPSPACE2, 10);
fsync(fd);
if (ENABLE_FEATURE_CLEAN_UP)
close(fd);
return 0;
}
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